© Copyright 2017 by The American Society of Tropical Medicine and Hygiene. We present a series of four pregnant women with Rocky Mountain spotted fever (RMSF) that occurred in Sonora, Mexico, during 2015-2016. Confirmatory diagnoses were made by polymerase chain reaction or serological reactivity to antigens of Rickettsia rickettsii by using an indirect immunofluorescence antibody assay. Each patient presented with fever and petechial rash and was treated successfully with doxycycline. Each of the women and one full-term infant delivered at 36 weeks gestation survived the infection. Three of the patients in their first trimester of pregnancy suffered spontaneous abortions. RMSF should be suspected in any pregnant woman presenting with fever, malaise and rash in regions where R. rickettsii is endemic.